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160                        EXTINCT POLYPROTODONTS                 CHAP; vi
Australia. The most interesting fact in connexion with the
Tertiary Polyprotodouts is the existence in South America of such
genera as Prothylacinus and Amphiproviverra, which are not
merely Polyprotodonts but definitely Dasyures, and not referable
to the Bidelphyidae.
These forms have been included in an order, SPARASSODGNTA.
But it is not by any means certain whether these forms are
rightly placed in the neighbourhood of the carnivorous Marsupials;
it is possible that they ought to be relegated to the Creodonta or
to their allies. Their structure is in fact somewhat intermediate
between those two groupa The teeth seem to be carnivorous and
Marsupial-like in form; but as already mentioned, in connexion
with the general structure of teeth, more than a single premolar
is replaced. These animals in fact, in so far as regards their
teeth, are midway between the Marsupials and the typical Eutheria,
The angle of the lower jaw is inflected, but the palate is not
marked by deficient ossification. At least this is not the case
with all the members of the group. Whether the small Micro-
"biotherium, which is made the type of a family, is rightly referred
here is not certain. This animal had palatine vacuities as well
as an inflected angle to the lower jaw.